1. Field of the Invention
The present invention relates to an artificial turf, comprising a backing and a large number of artificial grass blades which are fixed thereto, protrude substantially transversely thereof and are manufactured from plastic. Such an artificial turf is generally known and is used on a large scale for practising sports such as football, hockey, tennis, rugby, baseball, American football and the like.
2. Description of the Prior Art
The known artificial turf consists of a backing, for instance a fabric of synthetic yarns to which a large number of artificial grass blades is fixed. These artificial grass blades, which can be tufted or knitted to the back or co-woven therewith, protrude substantially transversely of the backing. The is artificial grass blades are generally manufactured from somewhat hard and smooth types of plastic, for instance polyolefins such as polyethylene, polypropylene or mixtures thereof, or polyamides such as nylon. The artificial grass blades thus form a relatively robust and wear-resistant ground for playing sport or games.
In order to form an artificial grass surface the known artificial turf is arranged on a firm substrate or base layer of for instance sand, asphalt, stone chippings, lava or other preferably moisture-permeable material. Particular types of artificial turf herein also have sand spread therein after laying thereof.
In order to be able to play on the surface in the same manner as on a normal grass field, it is important that the artificial turf surface has roughly the same properties, particularly in respect of aspects such as the behaviour of the ball on the surface. For this purpose the artificial turf surface must be somewhat resilient and able to dampen shocks sufficiently, which is also important in preventing injuries to joints. This is the reason that the known artificial turf surface is generally provided with a damping material. This damping material, for instance rubber or a polyurethane foam, can be arranged under the artificial turf, whereby the damping action is however not very direct.
Use is therefore frequently made of rubber in the form of grains or granulate, which is arranged between the artificial grass blades. These rubber granules, which in the case of an artificial turf surface with sand spread therein can be mixed with the sand, as for instance described in the U.S. Pat. No. 5,958,527, here therefore lie loose in the artificial turf. This has the drawback that it is not simple to obtain and maintain a uniform distribution of the damping over the surface of the artificial turf, since the rubber granules are per se not wholly identical and, when the field is used, will moreover be displaced and thus be spread unevenly. In the case of rainfall on a field with poor vertical drainage the granules can for instance be washed away to lower-lying parts of the field. In addition, the granules can come to lie on the surface, whereby they may adhere to the ball and the playing surface will furthermore become relatively rough locally. Also when the rubber granules are used in a surface with sand spread therein, there occurs in practice rapid separation of the sand and the rubber granules, whereby the damping will vary considerably over the surface.
The invention now has for its object to provide an artificial turf wherein these drawbacks do not occur. According to the invention this is achieved in an artificial turf of the above described type by a fibrous, inherently damping material arranged between the artificial grass blades and connected to the backing or the blades. xe2x80x9cInherently dampingxe2x80x9d material is herein understood to mean a material which is relatively soft and resilient per se, irrespective of its embodiment, while xe2x80x9cfibrousxe2x80x9d is understood to mean any elongate, slender embodiment of the material. Connecting the damping material to the rest of the turf prevents it being displaced and a uniform distribution thereof is thus ensured, which can moreover be adjusted and monitored during production of the artificial turf. In addition, the fibrous nature of the damping material also results in a further improvement of the damping action.
The inherently damping material is preferably a material different from the plastic from which the artificial grass blades are manufactured. The somewhat conflicting requirements of resistance to wear on the one hand and good damping on the other can thus be satisfied by a suitable choice of material. The inherently damping material is advantageously less stiff herein than the plastic of the artificial grass blades, so that, even in the case of corresponding material thicknesses, there still exist differences in damping between the artificial grass blades and the inherently damping material.
An artificial turf which is simple to manufacture and to lay is obtained when the fibrous, inherently damping material is arranged in the form of a large number of blades connected to the backing. These blades then preferably extend substantially transversely of the backing.
In order to prevent the playing characteristics of the artificial turf being affected by the damping material, the blades of the damping material advantageously protrude less far from the backing than the artificial grass blades. To this end the blades of the damping material can be shorter than the artificial grass blades, but it is also possible for them to be frizzed.
In another embodiment of the artificial turf according co the invention the fibrous, inherently damping material takes the form of a knit through which the artificial grass blades protrude. This knit is then preferably formed integrally with the backing, whereby the structure of the artificial turf is simplified.
The damping material, which is preferably moisture-absorbing so as to prevent injuries such as burns in the case of a xe2x80x98sliding tacklexe2x80x99, can be a natural or synthetic rubber, although a flexible plastic such as for instance a polyurethane can also be envisaged. Said materials can herein be applied in solid form or as foam.
In a variant of the artificial turf according to the invention of particularly simple structure, the inherently damping material is formed by the same plastic as that from which the artificial grass blades are manufactured.